Abstract:

Effects of grafting on the pepper fast chlorophyll fluorescence induction kinetics were studied under high temperature（45 ± 1）℃ and low temperature（4 ± 1）℃ stress in this study. The grafted pepper‘P205’or‘Yelimu’was used as a rootstock，and the self-rooted pepper‘Sandaojin’was used as a scion. Results showed that the fast chlorophyll fluorescence induction curve（OJIP）of self-rooted seedlings had significant changes with a decrease in J，I and P points after heat and chilling stress. JIP-test revealed a significant K phase. Under heat treatment，the ΔK values of self-rooted and grafted seedlings were more than twice higher than those under the chilling stress，indicating that the photosynthetic apparatus of pepper leaves were more susceptible to heat injury. Under heat and chilling stress，the self-rooted seedlings had the greater decrease than those of the grafted seedlings in maximum photochemical efficiency（F_v/F_m）and performance index（PI_abs）. The PI_abs was more sensitive to heat and chilling stress than F_v/F_m. For all the tested materials，the phenomenological energy fluxes per excited cross section（ABS/CS_m?TR_o/CS_m and ET_o/CS_m）and the density of RCs（RC/CS_m）were decreased，while the relative variable fluorescence at J-step（V_J），the dissipated energy flux per CS（DI_o/CS_m），the quantum yield for energy dissipation（Ψ_Do）and the total performance index（PI_total）were increased. All fluorescence parameters of self-rooted seedlings had significant difference compared to the control group. Rootstock‘P205’and‘Yelimu’were adaptable for heat and chilling treatment，respectively. The PI_total of grafted and self-rooted pepper increased sharply after high or low temperature stress，followed with a complete recovery at 25 ℃ after 4 h，suggesting that the photosynthetic apparatus of photosystemⅠ（PSⅠ）was less damaged than PSⅡ during the temperature stresses.

Key words: pepper, grafted, JIP-test, chlorophyll fluorescence kinetics, temperature stress